Printing cylinder and the like



Dec. 23, 1941. J. GGRIG 2,267,646

PRINTING CYLINDER AND THE LIKE Filed May 5, 1939 2 Sheets-Sheet 1 26 G 26 0 25 C4 b //7venz0P JEaqf G 0 7" /y Dec. 23, 1941. GR; 2,26%646 PRINTING CYLINDER AND THE LIKE Filed May 5, 1959 2 Sheets-Sheet 2 Patented Dec. 23, 1941 PRINTING CYLINDER AND THE LIKE Josef Giirig, Cologne-Junkersdorf, Germany, as-

signor, by mesne assignments, to the firm Eden A. G., Zug, Zurich, Switzerland Application May 5, 1939, Serial No. 272,026 In Germany May 5, 1938 2 Claims.

The present invention is concerned with the construction of printing members, especially printing cylinders, and is more particularly concerned with cylinders provided with a light sensitive coating or layer.

In the production of this kind of printing members, it is well known to enclose the coated cylinder by means of a transparent flexible sheet which carries the images to be copied onto the cylinder. In the following the sheet will be referred to as image-bearing sheet. It is further to be understood that by the expression image, I refer to all kinds of copying records, pictures or illustrations and the like, as well as text.

In thus manufacturing printing members, it

has hitherto been diflicult to attain a sufficiently firm and close contact between the images and the light sensitive coating of the printing cylinder.

Various methods and means have been proposed for improving the contact between image and cylinder. However, up to now either the results were unsatisfactory, or the methods and means were too complicated for practical use.

I have found that these difiiculties may be effectively overcome and that the desired object is attainable in a perfectly satisfactory manner and by simple means.

According to the invention, the edges of the image-bearing sheet after wrapping the latter around the cylinder, are sealed against said cylinder, the intermediate space between the sheet and the cylinder then being evacuated through one or several openings in the sheet, or at the edge of the latter. This results in causing atmospheric pressure to tightly press the sheet against the cylinder in all places, so that the copying process can be carried out in a faultless manner.

One object of the invention is to employ for the purposes described a transparent flexible image-bearing sheet with one or several holes for cooperation with a suction line. This suction line is preferably connected to the hole, or holes, by means of one or more separate flexible members, such as a suction head of soft rubber adapted to adhere tightly to the image-bearing sheet when pressed against the respective face.

The sealing off between the transparent sheet and the cylinder is suitably effected by glued strips. Such strips are, of course, to be fixed at the points at which the outer edges of the imagebearing sheet meet with the cylinder, as well as where the adjacent edges of the sheet meet when the mounting form is placed around the cylinder.

These adjacent edges of the sheet should not abut each other when the latter is wrapped around the cylinder, but in this stage of the process either a gap must be left between them, or they must overlap one another, in order to allow for the necessary free movement when the sheet is tightly fitted around the cylinder, and the air is evacuated from the intermediate space between the image-bearing sheet and the cylinder.

In order to ensure that no sealed hollow spaces or air-pockets form between cylinder and imagebearing sheet in the first stage of evacuation, from which it would then become impossible to evacuate the air, lands or the like are sometimes provided on the sheet around the positives to be copied, in a manner such that the formation of said closed hollow spaces is prevented and, consequently, the evacuation of the air from all places is ensured. It is therefore an important object of the invention to provide, for the purposes in question, an image-bearing sheet provided with lands or the like. These lands or the like may be formed integrally with the sheet or separate members, such as filaments'or wires, may be fixed on the sheet around the images, the former being applicable principally in cases where a large series of separate images of about the same size and distribution or location are to be copied. In other cases it is more suitable to use the latter method, 1. e., to surround the images by threads, wire, or the like, after fixing the records containing the images on the sheet, the threads or the like being fixed in any convenient manner.

For a more detailed description of the invention, reference is made to the attached drawings in which- Fig. 1 diagrammatically represents a printing cylinder in assembled form;

Fig. 2 is a longitudinal section of a printing cylinder with the image-bearing sheet attached.

Figs. 3 and 4 represent two modifications of the image-bearing sheet.

Figs. 5, 6, and 'I and Fig. 8 are respectively cross-sections, and a plan view, of various types of sheets with images; and Figs. 9 and 10 are respectively an elevation and a sectional view of a preferred suction head.

Referring first to Figs. 1 and 2, the printing cylinder l is provided with a light sensitive coating 2. Positives 3 are firmly held against the cylinder in contact with the coating by means of a sheet 4, the marginal edges of the sheet being fixed by glued strips 5 to the cylinder, whereas the adjacent edges of the sheet are fixed by glued strip or strips 6. Suction heads cooperate with openings in the sheet, connecting the space between the sheet 4 and cylinder l to the vacuum or pump lines 8, which lead to a vacuum chamber or to a vacuum pump (not shown).

The comparatively short image-bearing sheet l4 shown in Fig. 3 is provided with on marginal suction opening 15 only, whereas the mounting form 24 shown in Fig. 4 is provided with a plurality of openings 25 adjacent both margins, and with additional openings 26 in areas bearing no images. It will be understood that provision of these additional openings is only practicable when the sheet 24 is to be constantly used in connection with separate images of about the same size and/or arrangement.

As already mentioned, I provide the imagebearing sheet with lands or the like, in order to prevent the formation of air pockets. Figs. 5 to 8 show the sheet 34 with records 33 attached, lands being formed in the spaces intermediate the records 33 either by narrow strips 35, (Fig. 5) which may consist of artificial resin or other suitable material, or by wires 36 (Fig. 6) or filaments 3'! (Fig. 8). According to Fig. 7, the lands are formed integral with the sheet 34, and are designated by reference numeral 38.

For connecting the openings provided in the sheet to a suction line or pump, suitable suction heads may be used, a preferred type of head being designated at 4! in Figs. 9 and 10'. Head 41 may consist of soft rubber shaped to adhere tightly to the sheet when pressed against the same around the opening, or openings, of the sheet after the latter is sealed against the cylinder. Suction head 41 is connected to suction pipe 48, which may be provided with a valve or cook (not shown), so that by closing the latter, the subatmospheric pressure may be maintained in the space between sheet and cylinder even if pipe 48 be disconnected from the vacuum line or pump.

3 The invention may be used in the following manner:

First the images are applied to the imagebearing sheet (4 for example) and, if desired, strips 35 or filaments or wires 36 or 31 are fixed on the form intermediate the images, or a mounting form having integral lands 38 may be used. Then the sheet is tightly wrapped around the cylinder I, one of its edges being fixed thereon by a glued strip (not shown). Thereupon the sheet is smoothly spread and tightly pressed onto the cylinder, for example by means of a roller, a rod or the like (not shown). Then the remaining edges of the sheet are fixed by means of glued strips 5, 6, thereby air-tightly sealing the image-bearing sheet to the cylinder I. Now the soft rubber head 1 or 41 provided with the suction pipe 8 or 48 is placed over the opening or openings provided for this purpose in the sheet, and the air is evacuated by means of a suitable pump, thereby causing atmospheric pressure to effect a close contact between the images and the light sensitive layer 2 of cylinder I. Then the copying process may be carried out in any of the well-known suitable manners.

I claim:

1. For the production of printing members from cylinders provided with a light sensitive coating, an image-bearing sheet, said sheet consisting of flexible transparent material and provided with at least one suction opening and with projections on its inner face, said projections being located between the zones to be occupied by the records.

2. In combination with a cylinder having a light sensitive coating, records to be copied lying against said coating, a flexible mounting sheet curved around said cylinder and holding said records against the same, an adhesive strip extending longitudinally of said cylinder and air-tightly sealing the longitudinal edges of said mounting sheet to each other, and additional adhesive strips extending circumferentially of said cylinder and air-tightly sealing the other edges of said mounting sheet to said cylinder, said sheet having at least one suction opening.

JOSEF GGRIG. 

